This invention relates generally to processes for imparting desired patterns of surface depressions and protuberances or concavities and convexities (hereinafter referred to as surface "unevenness") to the surfaces of decorative materials or articles. More particularly, the invention relates to a process wherein a sheet having expansion-contraction deformability which differs with different regions thereof is caused to undergo expansion-contraction deformation, and a clear unevenness pattern corresponding faithfully to these regions is imparted to a decorative material layer in contact with the sheet.
Examples of processes heretofore known for imparting unevenness patterns on surfaces are a process wherein, by means of an embossing roller with a relief or embossed pattern on the surface thereof, the pattern is mechanically impressed on the surface to be embossed and a process wherein a material for constituting a decorative layer is poured into a metal mold. However, while the pattern can be formed faithfully according to the embossed pattern or mold by these processes, the roller, plate, or mold is expensive, and the production efficiency is poor. In many cases, furthermore, complicated accessory equipment and operation are required.
In addition, for producing decorative articles having unevenness patterns without using metal molds, there are processes such as that wherein expansion or foaming is caused regionally or the degree of expansion is regionally varied. In general, however, these processes are accompanied by the problem of limitation of the materials which can be used therein.
As a result of our various studies previously directed toward a simple method of forming any desired unevenness pattern, we have found that, by utilizing the characteristic of various resin sheets, films, and the like of deforming by expansion or contraction when they contact a liquid having affinity therefor by providing on a sheet or film of this character regions which are not subject to the effect of such a liquid or regions differing in the degree in which they are affected by the liquid, for example, by printing, and causing the sheet or film to contact a decorative material layer containing an ingredient which gives rise to expansion or contraction deformation (hereinafter referred to simply as deformation) in the sheet or film, an unevenness pattern corresponding to the printed pattern is imparted to the decorative material layer. On the basis of this discovery, we have developed a process for producing decorative articles, as disclosed in the specification of Japanese Patent Laid Open No. 91061/1977.
More specifically, this process for producing decorative articles comprises the steps of superposing on a decorative layer prior to treatment a sheet provided with regions subject to deformation and regions not subject to deformation due to ingredients constituting the decorative layer, and/or regions having differences of degree of susceptibility to deformation, and then carrying out an appropriate after-treatment, depending on the ingredients constituting the decorative layer, thereby to cause the formation on the decorative layer of unevenness corresponding to the various regions. By this process, if a wood grain pattern, for example, is printed on the sheet, an unevenness pattern corresponding to this wood grain pattern can be imparted to the decorative layer composed of, for example, a concrete composition.